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  Failsafe injected adhesive jointFailsafe injected adhesive joint description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070261787, Failsafe injected adhesive joint. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001]This invention relates in general to a method for joining structural composite parts or composite to noncomposite parts using an adhesive injected into the joint with failsafe features BACKGROUND OF THE INVENTION [0002]One method of joining two structural members together is by the use of an adhesive at the interface between the two members. The adhesive typically transfers shear load between the members via an adhesive bond. This bond is critical, and requires considerable effort in both manufacturing and inspection. Despite the best efforts, use of adhesive bonds in aircraft and other primary structures is very difficult to certify, due to the catastrophic failure mode of a debonded joint. The only proven way around this pervasive problem is to bolt the bonded joint together with mechanical fasteners, which removes many advantages of the bonded joint, particularly when the joined members are composite. [0003]It is important during the bond assembly process that the adhesive extend throughout the bonding surface, preferably at a uniform thickness. This is difficult to accomplish at times, leaving spaces or areas that do not have adhesive. Speeding the process up would be desirable to reduce costs. SUMMARY OF THE INVENTION [0004]In this invention, elongated, undulating recesses are formed in the bonding surfaces between two members to be joined. The recesses align with each other to define an elongated cavity when the bonding surfaces are placed against each other. Adhesive is injected into the cavity formed by the recesses. When cured, the adhesive both bonds the members together, and forms interlocking resin keys that carry load in case of bondline failure. [0005]Preferably, one of the members is a composite skin panel with a molded holes and recesses while the other member is either composite with a similar molded recess or a metallic member with a machined recess. The recesses are preferably shallow grooves that are rectangular in cross section, and undulate both in direction and width, forming a sinusoidal or diamondback pattern. This geometry provides locking of the keys in all directions, as well as a generous flow path and ample cross sectional areas to allow high shear loads in the adhesive keys. Preferably the recesses extend from one end of the assembly joint to the other end. Preferably, the injection ports occur at the wide areas of the grooves, to permit easy flow at the entry and exit ports for the adhesive. [0006]As the adhesive flows through the grooves, it will completely fill the channel until it exits the next injection port, at which time the injection is continued from that same port. This operation is completed when the bond line is filled, at which time the ports can be plugged to prevent adhesive loss. [0007]In one embodiment, the structural members comprise flat surfaces that are joined orthogonally to each other. These members may be analogous to a wing or fuselage skin with an underlying spar or frame substructure. One member contains a clevis shaped feature, while the other member is of a blade configuration. There are bonding areas on both sides of the blade, and the grooves are repeated on both sides. The injection port accesses the joint from below the clevis, and engages the grooves in both the clevis and blade feature of both members. [0008]Prewoven composite reinforcements (preforms) can be used to form the clevis features easily, and can be cured along with the skin portion of the outer member. The blade member can be a simple flat laminate portion of the underlying substructure. Both members can use a simple mandrel tooling to form the recess in each side of the joint during part layup/infusion and cure [0009]Another possible joint in which this invention can be employed is a lap shear configuration. This is a very common type of joint that is used in joining two like members such as in a skin to skin, frame to frame, or even truss attachments. In this case, there is one bond line formed when two members are lapped over each other. There is only one groove in each member, and they are created, aligned, and injected in a similar manner as the clevis configuration mentioned above. [0010]This invention completely solves the prior art bonding problems by providing an alternate means of load transfer in case of bond failure, thereby enabling a failsafe feature in the joint that does not require mechanical fasteners. It is compatible with composite laminates and even metal parts, provided the recesses can be economically fabricated. Typically, recesses and holes can be molded in during the cure process of resin matrix composite, particularly in the case of processes that infuse dry fabric or preforms. [0011]Injecting adhesive from outside the structure into a structural bonded joint is a vast improvement of current techniques. Fitup and surface preparations of the bonding surfaces are no longer critical. The only critical processes that must be verified is that the adhesive has properly filled out all the recesses and is fully cured. This verification is easy to do, since the adhesive samples can be taken from the exposed injection ports, and filling of the cavities can be verified by X-ray or techniques commonly used for structures. [0012]Also, the invention allows dry assembly with sequential bonding of individual joints. This feature allows large structures to be joined over a period of time, without regard for the cure time of the adhesive. BRIEF DESCRIPTION OF THE DRAWINGS [0013]FIG. 1 is an exploded perspective view showing an example of a structural member, a preform, and an aircraft skin assembly in accordance with this invention. [0014]FIG. 2 is a transverse sectional view of the structural member of FIG. 1. [0015]FIG. 3 is sectional view of the assembly of FIG. 1, taken along the line 3-3 of FIG. 4, and showing adhesive being injected. [0016]FIG. 4 is a transverse sectional view of the assembly of FIG. 1, after or during the injection of adhesive. [0017]FIG. 5 is a sectional view of the assembly of FIG. 1, taken along the line 5-5 of FIG. 4. [0018]FIG. 6 is a schematic view of a weave pattern of the woven preform of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION [0019]Referring to FIG. 1, a structural member 11 is shown being joined to a second member 13, which typically comprises the skin of an aircraft. In one example, an interface member 15 provides an interface to bond structural member 11 with skin 13. In one embodiment, interface member 15 comprises a woven preform, however other members could alternately be used. Continue reading about Failsafe injected adhesive joint... Full patent description for Failsafe injected adhesive joint Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Failsafe injected adhesive joint patent application. Patent Applications in related categories: 20090000735 - Lamination device method for flexographic plate manufacturing - An apparatus and related method for laminating a masking film onto a pre-press flexographic printing plate to place the plate in optical contact with the film by applying a balanced, non-distorting force to the flexographic printing plate and masking film. This method includes laminating the pre-press flexographic printing plate with ... ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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